This invention relates generally to an internal combustion engine, the combustion of which is improved.
In regard to combustion occurring in internal combustion engines, it is known in the prior art for controlling the various exhaust gases to be advantageous to burn NO.sub.x (oxides of nitrogen) using an excess of fuel so as to lower the average temperature, and to burn off CO (carbon monoxide) using a thin fuel/air mixture.
Another method for decreasing the NO.sub.x and CO consists in maintaining the rich mixture at a high temperature of combustion to control NO.sub.x, and secondly to accelerate the oxidization reaction by means of additional air to decrease CO when the temperature is somewhat lowered by progress of the combustion.
According to these proposals, there has already been provided a practical engine in which mixtures supplied as lamina flows are generated and burnt in a form of dual combustion. Another engine is also known having a second chamber, its combustion chamber being divided into a main and an auxiliary chamber, the mixtures being injected into the latter.
These engines have problems in regard to (i) quantity of HC which remains unevaporated and (ii) CO generated by the burning of the non-evaporated HC, because the combustion of these engines is intermittent and performed under a limited rise of temperature.
To find a countermeasure which does not lower the thermal efficiency, it is to adopt single combustion.
In the operation which generates HC and CO through combustion, under present conditions, the gases include a great deal of mixture which flows from the part of the top ring of a piston and which composes quenching zones on the inner wall surface of the cylinder and the upper surface of the piston, during the process of combustion. In an exhaust stroke, a large quantity of waste gases flows out immediately after the valve is opened. HC in the gases is mainly drawn off from a quenching zone on the inner wall surface of the cylinder head. In the later portion of the exhaust stroke, HC and CO on the wall surfaces of the piston and cylinder are carried to the valve while it is open, so that extremely enriched waste gases are exhausted.
It is therefore obvious that the avoiding of generation of HC and CO is impossible at present without a countermeasure which prevents formation of quenching zones on those wall surfaces.